Computers are designed to process, store, and retrieve data according to a computer program. Because computers are becoming faster, more powerful, while at the same time, more affordable, they are increasingly finding uses in various fields. Not surprisingly, one field in which computers have successfully been employed is that of word processing and desktop publishing applications.
In the preparation of textual documents, computer applications for word processing and desktop publishing offer the user great versatility in its appearance and in any subsequent editations. Features such as the size, font, layout, format, alignment, outline, and graphics of a document is readily under the control of the user. In addition, the user has control over the page numbering, footnoting, indenting, underlying, embolding, shadowing, and italicizing of certain text within the document. Moreover, standard word processing and desktop publishing applications provide the user with handy edit commands such as finding, inserting, deleting, cutting, pasting, and spell checking. Changes to the document can be made globally or only to selected portions. The completed textual document can be electronically stored (e.g. floppy disk drive, hard disk drive, optical disk drive) and retrieved or updated at a later time. Indeed, access to the textual document can be shared by multiple users on multiple computer terminals by utilizing a file server on a computer network. More commonly, a hard copy of the finished textual document is made by printing it out on paper.
Traditionally, the user interlaces with the computer system by means of a QWERTY keyboard. Textual data is entered into the computer system by typing characters (e.g., letters, numbers, and symbols) on the keyboard. The entered characters are temporarily saved in the computer's memory and are displayed on a cathode ray tube (CRT) display device. Thereupon, the user may elect to enter more text, edit the existing text, write the document onto a storage medium, or print the document.
In typical prior art computer systems, the user enters a character into the computer system by depressing or "typing" a key on the keyboard corresponding to that character. By depressing that key, the user causes an electrically encoded signal representing that key's character to be generated and sent to the computer. Some of the more widely used character encoding schemes include ASCII and EBCDIC. Each character has its own unique code. Based on the codes received from the keyboard, the computer generates the glyph corresponding to that code. The glyph is displayed on the CRT display screen or printed on paper. For example, by depressing the "A" key on the keyboard, a hexadecimal code of "61" is generated and sent to the computer. The computer then generates a glyph "a" corresponding to that code. Thus, typical prior art word processing and desktop publishing applications essentially have a one-to-one correspondence between each character and a glyph representing that character.
One disadvantage with the prior art is that this one-to-one correspondence results in a rather inflexible system. Under such a system, the number of different glyphs is limited to the number of characters available. For example, given an 8-bit encoding scheme, there can only be 2.sup.8 =256 different characters. Consequently, a font (i.e., a collection of glyphs usually having some element of design consistency in their appearances) is limited to only having 256 different glyphs. Some of the more stylistic, artistic, and visually appealing fonts require a greater variety of glyphs.
Furthermore, a related disadvantage with the typical prior art method for rendering text is that, in order to add a new glyph, a character code must be assigned to each of the new glyphs, to provide the user access to those glyphs. Hence, valuable character code space is consumed if additional glyphs are desired.
Another problem associated with typical prior art approaches for rendering text is that the character set might be too small to fully render a written language. Given a 256 character set, there are enough characters to adequately represent the capital and lower case 23 letters (a-z) of the Roman alphabet, Arabic numerals 0-9, punctuations, and other various symbols comprising most modern western and European languages. However, other types of script, such as Arabic and Hindi, can have upwards of 500 different contextual forms for a fancy font. Past approaches have been to select the 256 most important forms for presentation. Consequently, prior art text rendering methods have encountered problems when dealing with multilingual applications.
Yet another problem associated with prior art text rendering methods is that, in most instances, the person who designed the computer system also specified the character set. A subsequent font designer, who wishes to design a font for that computer system, is constrained to the pre-determined character set. Otherwise, there would not be a mechanism for accessing that particular glyph. As a result, the font designer is limited to designs which were anticipated by the computer designer.
Thus, what is needed is a textual rendering scheme whereby there can be a great number of different glyphs for a given character set. Thereby, the computer's range of things which can be rendered is greatly expanded.